1. Field of the Invention
The present invention relates to a structure of a transfer pipe for transferring dried concentrate by compressed air and relates also to a breakage detecting method applicable upon breakage of the transfer pipe having such structure by wearing caused by dried concentrate.
2. Description of the Related Art
Concentrate available through concentration is conventionally dried by heat for the purpose of saving heat energy in the ore refining process, and facilitating such handling as feeding of ore to the furnace and conveyance thereof, and preventing a decrease in reactivity caused by moisture. Particularly in the case of a flash smelting furnace, strict drying is applied.
A concentrate drying facility for drying copper concentrate to be fed to a flash smelting furnace in a copper smelting plant has a flash drier and a steam drier. FIG. 1 illustrates a steam drier side drying equipment 100 having a steam drier 105 forming a part of the concentrate drying facility.
As shown in FIG. 1, copper concentrate S is distributed by a distributor 101 to a flash drier side drying equipment 100A and a steam drier side drying equipment 100. Description of details of the concentrate drying equipment 100A on the flash drier side is omitted here.
Concentrate S distributed to the steam drier side drying equipment 100 is conveyed while being weighted on a steam drier feed conveyor 102. Concentrate from the steam drier feed conveyor 102 takes out coarse concentrate through a shaking screen 103 to outside the system.
Concentrate S having a prescribed size screened by the shaking screen is charged into a steam drier 105 on a shaking feeder 104.
In the steam drier 105, the concentrate S is dried by use of steam generated in a waste heat boiler of the flash smelting furnace. The dried concentrate S is discharged from the steam drier 105 by operating a rotary valve 106. On the other hand, steam produced upon drying the concentrate S is subjected to dust removal by a bag filter 107, and released to the open air via an exhaust fan 107a and a stack 107b. 
The concentrate S dust-collected by the bag filter 107 is conveyed by a screw conveyor 108 and discharged from the bag filter 107.
The concentrate S discharged from the steam drier 105 and the bag filter 107 is then sent to a service hopper 110 of an air transfer equipment by an eprobator 109. Then, the concentrate S is sent from the service hopper 110 to a lift tank 111.
The lift tank 111 into which the concentrate S has been charged is then tightly closed, and fed with compressed air from a compressor 112 to pressurize the interior of the lift tank 111. Air compressed by the compressor 112 is sent through a drier 113 and a super-line filter 114, retained in a receiver tank 115 and then supplied to the lift tank 111. Then, the interior of the lift tank 111 is pressurized.
Subsequently, the concentrate S is air-transferred to an existing dried ore hopper 200 through the transfer pipe 117, together with compressed air by opening an air-transfer valve 116 installed on the lift tank 111. The thus air-transferred concentrate S through the transfer pipe 117 is collected in a dust chamber 118 and a bag filter 119 installed before a dried ore hopper 200, dust-collected, and sent to a dried ore hopper 200.
The concentrate S dried at the steam drier 105 and collected in a dried ore hopper 200 as described above is then fed to the flash smelting furnace 201 via an LI feeder which is a concentrate feeder.
Conventionally, the transfer pipe is a straight pipe or a bending pipe, and is usually a steel pipe. As required, a wear-resistant ceramic hose is used as a bending pipe.
As described above, the dried copper concentrate S is transferred by compressed air through the transfer pipe 117, and the dried copper concentrate causes wear of the interior of the transfer pipe 117, may spout and splash in the open air. Occurrence of such a trouble causes problems in operation as well as in environments.
The present inventors therefore improved the structure of the transfer pipe 117, and made development efforts of warning means for a case where the transfer pipe 117 is broken by any chance.
For example, Japanese Patent Application Laid-Open No. 58-19531 discloses a double pipe breakage detecting method in a double pipe used as a pipeline for transporting fluid such as petroleum.
This double pipe breakage detecting method comprises dividing an annular space formed by an inner cylinder and an outer cylinder into a plurality of spaces, and filling the thus divided annular space with a liquid (water). When the inner cylinder is broken, the steps include causing the pressurized transporting liquid in the inner cylinder flow into the annular space, increasing the pressure in the annular space, pressurizing the water in the annular space to raise the liquid level in a liquid level monitoring drum, and activating an alarming device. When the outer cylinder is broken, causing water in the annular space to flow out, causing water in the liquid level monitoring drum to flow into the annular space, lowering the liquid level in the liquid level monitoring drum, and activating the alarming device.
In the double pipe breakage detecting method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 58-19531, the double pipe used itself is a pipeline prepared from a usual double pipe-structured steel pipe or the like.
Such a double pipe cannot be used as a transfer pipe 117 which transfers granular or powdery high-temperature dried concentrate by compressed air, not a liquid such as petroleum to be covered by the present invention. The double pipe breakage detecting method of filling an annular space formed by an inner cylinder and an outer cylinder composing the double pipe with a liquid such as water is not applicable as warning means of a transfer pipe 117 in a concentrate drying equipment 100 which transfers a high-temperature dried concentrate by compressed air, since, when the inner cylinder is broken by accident, the liquid such as water is mixed with the dried concentrate which absorbs water, thus exerting adverse effects such as adherent residue on the subsequent facilities.